The present invention relates to stretchable sleeve labels used in labeling containers and, more particularly, with printed sleeve labels with a protective coating over the printing.
Sleeve labels have replaced adhesive labels on many products such as plastic jugs, bottles, drums and propane/butane cylinders. Sleeve labels are made from plastic films printed and formed into sleeves which can be placed over the container. They differ from "shrink wrap" packaging in that sleeve labels are stretched and placed over the product or container as a sleeve. When released, the sleeve relaxes toward a memory condition, securing the sleeve to the product without heat or chemical treatment. Sleeve labels can be easily attached and removed from the container without the use of adhesives. Sleeve labels promote recycling of containers since the old labels can be removed quickly without the residue of adhesives. Printing, fabrication, insertion, and removal are easily automated, resulting in low cost and good product flexibility. The printing methods used in sleeve labels allow high quality printing and graphics.
A common problem with sleeve labels is smearing of the inks printed on the film surface. Another problem is mechanical damage such as scuffing, scratching or abrading the printed surface of the sleeve label, degrading the appearance of the label. These problems are especially apparent when solvent containing liquids are contained in the packaging. The packaging is often heavy, increasing the mechanical stresses and loads during shipping and handling. Reversing the printing surface so that the printed surface is on the inside of the sleeve protects the printed surface from some mechanical damage. However, smearing still occurs due to solvent spillage from the product or from other sources. This is especially a problem when solvent base inks are used in the printing as they are readily dissolved by many solvents.
In the past, ultra violet (UV) curable inks have been used. The UV curable inks are resistant to most solvents, but are expensive and complicate ink inventory requirements. They also do not provide mechanical protection of the ink surfaces.
A second solution used in the past is to laminate a second plastic film over the printed surface. This method allows use of solvent base inks and provides protection from solvents as well as mechanical protection. However, laminating is a complicated and expensive process limiting its use.